It's not that companies are charging arbitrarily different amounts. They package features and levels of service or support differently for bespoke contracts, and that makes some of them cost more.

Any email list that failed to observe this would not be useful other than for the small companies looking for the feature/price floor.

Within reason, I personally am not offended by small variations based on legitimate negotiating for larger volumes (or even smaller volumes). I feel like most places will give you at least a bit of a discount if you offer something in return like enough volume to make it less hassle to sell to you.

Or if you just ask... I've definitely gotten 5-10% "discounts" multiple times just by asking if they can give me one. I figure this is the "wasn't price sensitive enough to ask" surcharge.

But if the prices were super random feeling yeah, for sure. I haven't personally run into more than a ~5-10% variation myself usually.

I think the only time I hear about it is when I get a price from a vendor, turn them down, and then have them come back with an offer for the same thing at 25% off. At that point they're kind of highlighting that their pricing is 25% higher than it needs to be for them to make a healthy profit so while I might take them up on it (once) I'm extremely likely to find a new vendor.

I've definitely done that before with a company that had dramatically overpriced high speed cameras. We kept ordering from them because we didn't want to worry about changing the brand. I doubt we'll order from them again.